Safety device fob electrical conductors



(No Model.)

' J. MARX.

SAFETY DEVICE FOR ELECTRICAL GONDUGTORS. No. 471,302. Patented Mar 22, 1892'.

lloaiupfiiilifi .of Nauheim, Germany,

UNITED STATES PATENT OFFICE.

JULIUS MARX, OF NAUHEIM, QERMANY.

SAFETY DEVICE FOR ELECTRICAL CONDUCTORS.

SPECIFICATION forming part of Letters Patent No. 471,302, dated March 22, 1892.

Application stun, 6,1891. set-in No. 398,567.

(No model.) Patented in England April 2'1, 1890, 110- 6,267; in fi l l ptember 1, 1890, No. 7,486 in Switzerland February 2, 1891. No. 847; in Austria-Hungary February $189110, 6,590 and No. 25,666; iu'Belgium February 9, 1891, R0. 1891, No. 209,049

70,621; in Italy February 13,

1891, No. 416, and in France October 22,

To all whom it may concern:

Be itknown that I, JULIUS MARX, a resident have invented new and useful Improvements in Safety Devices for Electrical Conductors, (for which I have applied for the following foreign patents: in England, No. 6,267, dated April 24, 1800; in Germany, No. 7,486, dated September 1, 1890; in France, No. 209,049, dated October 22,1891; in Switzerland, No. 347, dated February 2, 1891; in Austria-Hungary, dated February 3, 1891,No. 6,590 and No. 25,666; in Belgium, No. 70,521, dated February 9, 1891, and in Italy, No. 416, dated February 13, 1891,) of

which the following is a specification.

According to my invention the connection of electrical conductors is effected by means of a mixture or compound of finely-divided conductive material and a material which forms a means of oonglomerating the finelydivided conductive material and which is fusible or softened when an undue amount of heat arises in the electric circuit. As the .conductive material I prefer for ordinary purposes to use finely granulated or powdered carbon or graphite, and as the conglomerating material I prefer to use wax, such as paramne wax'or stearine or pitch or resin; butI do not limit myself to these precise materials.

For instance, for high temperatures a glass or enamel of a low melting-point can be used. The said mixture or compound of materials possesses the quality of softening if the conductors should become unduly heated, and when in that state the said compound becomes less conduct-ive or a non-conductor. This quality renders the mixture or compound applicable as a safety means for protecting electrical circuits from abnormal heating of the conductors, and it can therefore be used in place of the safety-fuses hitherto employed, as when it has become softened by undue heating not only is the supply of current diminished or discontinued, but the mixture or compound remains in place, (being contained in any suitable frame, box, or retainer,) and on cooling recovers its conductivity and therefore acts automatically to regulate or reestablish the' circuit. By proportioning the relative quantities and mass of the materials themixtu re or compound may be made to become softened and its conductivitylowered or discontinued in accordance with any amount of current against which it is desired to protect the circuit.

The following is a description of the mannerin vhich my invention maybe carried out, although I do not limit myself to the precise details which I shall describe. reference being had to the accompanying drawing,whioh shows a central section of my device.

Powdered graphite is mixed with molten parafiine wax, and the mass while in a state in which it can be molded is introduced (preferably by compression) into a frame or receiver, or the mass is made into the desired shape and size (for example, into a rod) and is then inserted in a tube made, preferably, of glass, porcelain, or other non-conductor. This is shown in the accompanying drawing, where the said mass is marked a, is marked 6. At each end of the tube 1) there is a small space, in which spaces are placed the metallic disks 0 0, having connected .to them the Wires (Z d to be afterward connected with the rest of the circuit. The disks 0 a should be pressed against the mass while it is still in a moldable condition. I prefer to make the disks somewhat smaller than the tube 1), so that I am able to place some of the materiel a around the said disks to insure good contact. The remaining spaces are filled up, as at e c, with plaster-of-paris or some other cement, or by any other suit-able means. To make good the contact of the conductors with the material a, disks 0 c' with extended surfaces of contact with the material a-such as, for instance, with points, as at f, or other projections or grooves, or a coil, as at g; or I may connect the mass and the wires by means of a metallic brush or not. If in using not it isrolled together with the material a, a very good contact is obtained. The tube Z) may be a metallic pipe, if desired; but then it must be lined with an insulator.

The size and shape of the device will of course be in accordance with the conductors and with the place in which it is to be used. For powerful currents, for instance,,a large and the tube too size and flat form are very suitable. The more powerful the electric current employed in the circuit the more will the length be reduced and the diametoror th-icknessincreased, as ofi course the diameter and length should be in accordance with the effects of the electric current.

The quantity of'paraliine (or the like) employed in the mixture should be such as to cement the grains of the conductive powder; but there must not be so much of the paraffine (or the like) as to make the material inconductive.

When the device is in use, the electric current will pass as 1011 g as it does not rise higher than to the degree the device isintended for;

but as soon as' the current exceeds that degree the material a is heated, so that it becomes less conductive, and the hotter it gets the less conductive it becomes, until when it becomes soft enough it interrupts the current. Under ordinary circumstances. the material should not get more than sufliciently warm to conduct only the current for which it is intended, and unlike the ordinary safety devices it does not necessarily cause a complete interruption of the current, while at the same time it does not admit more calculated or desired for a certain circuit.

Ilaving described my invention, what I claim as new, and desire to secure by Letters Witnesses ALvEsTo l. Hoses,

7 J EAN GRUND.

current than is 

